same issue to me, remove WP-Mail-SMTP also can’t help, any others suggest ?
im using plug in as below:
Akismet Anti-Spam
All In One SEO Pack
Better Search Replace
Contact Form 7
Easy WP SMTP
Flamingo
Google Maps Widget
Google XML Sitemaps
Huge IT Slider
Hyper Cache
Influence Plus
Jetpack by WordPress.com
Master Slider
Page Builder by SiteOrigin
Quick Page/Post Redirect Plugin
SiteOrigin Widgets Bundle
Slider Revolution
The Events Calendar
WordPress Importer
WP Google Maps
WPBakery Visual Composer
